Drain valves are certainly well known in the art and have long been used in connection with controlled drainage of accumulative liquids within containers. In a fuel/water separator, for example, it is important to drain the heavier water from the container which contains a lighter fuel atop water. One prior art device which accomplishes this task is shown in U.S. Pat. No. 4,440,193 to Matheson. In this prior art device, two passages are provided to the sealed container, one for liquid and the other for air. The purpose of these two passages is to prevent a vapor lock condition from occurring and allowing residual liquid to drain out through the liquid passage. When this prior art valve is open, the liquid passage opens first and, in a vacuum system, allows air to be drawn up through the passage creating bubbles in the accumulated water which tend to agitate the fluid at the liquid and water interface thereby mixing the two. This prevents proper drainage since the fluids are no longer separate.
The present invention solves this problem of fluid agitation during draining while allowing for relief of a vacuum which would occur during draining and preventing vapor lock. It also provides a single drain port for the collection of water which may also include fuel.